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IRS notice decoder · Corrections the IRS made

CP21A: the IRS changed your return and you owe

A CP21A says the IRS made changes to your return and you now owe. Find out what changed, then pay or disagree by the date on it.

By the Carry Forward Learning team Reviewed by Hunter Nottingham, JD, CPA

No dated figures Checked Review by

CheckedOct 19, 2026

What a CP21A means

A CP21A means the IRS made changes to your tax return, and you owe a balance because of them. source 1

The IRS page doesn't list what the changes were; the notice does, and the number printed on it is where the IRS says to ask. source 1

We'd never pay one of these blind. Know what changed first.

The date that counts

Pay by the date printed on your notice. The IRS says interest accrues on what isn't paid by the date on the payment coupon, and a late-payment penalty applies; the penalty may be removed in some situations if you contact the IRS by the due date. source 1

Why people get one

  • The IRS adjusted an item on your return, and the adjustment left a balance.

First steps

  1. Find what changed. The IRS says to call the number printed on your notice and say you got a CP21A with a balance due and need to review your account, with the notice and return in front of you. source 1
  2. Check your IRS online account, typed in yourself at irs.gov, to see the notice and your balance or payments.
  3. If you agree, pay by the date on the notice. The IRS suggests paying online so it arrives on time. source 1
  4. If you can't pay in full, look at a payment plan, a temporary collection delay or an offer in compromise. source 1
  5. Correct your own copy of the return for your records. source 1

What not to do

  • Don't pay before you know what changed and whether it's right.
  • Don't pay or send documents through a link or phone number in an unexpected email or text. Use irs.gov, typed in yourself.
  • Don't let the payment date slide. Interest and the late-payment penalty keep building. source 1
  • Related CP22A A look-alike notice: the IRS changed the return and a balance is due.
  • Related CP11 A correction notice for a math error that leaves a balance due.

Keep reading

Questions

How do I find out what changed on my CP21A?

The IRS says to call the number on your notice. source 1

What if I disagree with a CP21A?

The IRS says to call the number on your notice. source 1

Will I be charged interest and penalties on a CP21A?

Interest, yes, if you don't pay in full by the date on the payment coupon. A late-payment penalty applies too, though it may be removed in some situations if you contact the IRS by the due date. source 1

What if I think the CP21A is identity theft?

The IRS says to call the number on your notice and points to its Identity Theft Central page. source 1

Sources

  1. IRS, Understanding your CP21A notice (updated August 11, 2026) (external site) checked Oct 19, 2026

Every rule on this page comes from the IRS page in the list, read on the date shown. Your notice itself is the final word on its own dates and amounts.